Contact lenses provide a means for vision correction for a wide range of consumers. The advantages of contact lens wear are numerous. Improved convenience and improved appearance in comparison to spectacle glasses are probably the two most important advantages to most consumers. However, contact lenses require stringent care regimes in order to ensure comfort and avoid ocular infections. Proper care of contact lenses typically requires the consumer to periodically clean and disinfect the lenses, to prevent infection or other deleterious effects on ocular health which may be associated with contact lens wear.
One lens care system is the use of multiple-purpose solutions to clean, to disinfect, and to rinse contact lenses. These systems typically comprise a small amount of one or more antimicrobial agents and have been dominating most of the lens care market. Such popularity is most likely derived from the easiness and convenience provided by these new systems to consumers. In order to achieve a satisfactory disinfecting result, a contact lens has to be in a multiple-purpose solution for a sufficient time period. But, patients do not have a direct way to determine if their lenses have been in the lens care solution long enough to disinfect the lenses. In addition, currently available multi-purpose lens care solutions have little efficacy toward organisms like Acanthameoba, the species of which can cause keratitis, a painful vision-threatening infection of the cornea, and fatal granulomatous encephalitis in humans.
Another lens care system is hydroge peroxide-based lens care systems, for example, as described in patents and patent applications, such as, U.S. Pat. Nos. 4,585,488, 4,748,992, 4,899,914, 5,011,661, 6,440,411, 5,089,240, 5,196,174, 5,275,784, 5,468,448, 5,558,846, 5,609,264, 5,609,837, 5,958,351, 6,945,389, 4,812,173, 4,889,689, 5,523,012, 5,576,028, 5,807,585, 5,462,713, 5,591,397, 5,312,586, US 2011/0114517, and EP0124461 (herein incorporated by references in their entireties). However, hydrogen peroxide in these lens care systems is toxic to the cornea and thereby must be neutralized before lenses can safely be worn by a patient. Hydrogen peroxide typically is neutralized by adding a catalyst either during the disinfection process (i.e., one-step involving use of a platinum-coated disk or soluble catalase tablet) or afterward (i.e., two-step involving the addition of a catalase or a reducing agent after a designated disinfection time). The study of Hughes and Kilvington indicated that the commercially available hydrogen peroxide-based, one-step lens care systems has low or no activity against the cysts of Acanthamoeba species under study because of insufficient exposure time, whereas the commercially available two-step systems can have at least a 3-log kill after 4 hours of exposure (R. Hughes & S. Kilvington, “Comparison of Hydrogen Peroxide Contact Lens Disinfection Systems and Solutions against Acanthamoeba polyphaga,” Antimicrobial Agents and Chemotherapy, vol. 45, no. 7, pp. 2038-2043, July 2001). However, one disadvantage associated with the use of a two-step system is that a patient may inadvertently fail to neutralize hydrogen peroxide or prematurely remove lenses from the system, thereby suffering pain and trauma caused by hydrogen peroxide introduced into the eye.
Other methods for cleaning/disinfecting contact lenses have been reported that involve use of oxidizing agents and different neutralizing mechanisms.
For example, U.S. Pat. Nos. 5,462,713 and 5,591,397A describe a method for rapid disinfection of contact lenses, based on the combination of an oxidizing agent (i.e. peroxide, hypochlorite, ora precursor thereof) and a reducing agent (e.g., potassium iodide) and a neutralizing agent (e.g., ascorbate) for neutralizing Iodine generated through the reaction between the oxidizing agent and the potassium iodide.
U.S. Pat. No. 5,312,586 describes a method for rapid disinfection of contact lenses, based on using a peroxygen or hypochlorite compounds to disinfect the lenses and subsequently using active carbon to deactivate the peroxide or hyperchlorite.
GB2094992A describes a method for disinfecting contact lenses, based on hypochlorites generated through an electrical current and subsequently neutralized by its slow reaction with oxygen over a long period of time (e.g., overnight) or by using a platinum catalyst or a reducing agent in a short period of time.
GB1484972A describes a method for disinfecting contact lenses, which comprises contacting a contact lens with a solution including hypochlorite ions in an amount effective to kill pathogenic microorganisms and thereafter reducing all the hypochlorite to chloride with a reducing agent (e.g., sodium thiosulfate). The method of GB1484972 can be performed by using a tablet consisting of a top layer comprising a hypochlorite salt (i.e. sodium hypochlorite) and a bottom layer surrounded by gelatin and comprising a reducing agent (e.g., sodium thiosulfate) which is released after a certain time (e.g., about 30 minutes) needed for disintegrating the gelatin.
U.S. Pat. No. 5,451,303 describes a method for cleaning and disinfecting of contact lenses that involves placing a contaminated lens between an electrochemical oxidant-reductant pair (e.g., one being an oxidant in a gel and the other being a reductant contained in another gel) that have different oxidation potentials that generate an electrochemical potential difference across the lens sufficient to cause charged deposits to be removed from the lens.
JP2669690B2 describes a method for cleaning and sterilizing contact lenses which involves immersing a contact lens in an electrolytic solution which does not generate a hypochlorite by electrolysis and passing a DC current through the electrolyte solution so as to remove proteins and microorganisms.
EP0124461A1 describes a method that involves placing the lens in a solution an oxidant (e.g., hydrogen peroxide) to kill microorganisms, then placing in a second agent (e.g., hypochlorite or dichloroisocyanurate), which will degrade into products that are harmless for the eye.
WO 2013056165 describes a complicated lens cleaning system which functions as a two-step hydrogen peroxide system while, for the user, it functions as a one-step system. A system of WO 2013056165 comprises a reservoir for holding a hydrogen peroxide solution, a complex base that is coupled to the reservoir to insure a hermetically closed reservoir environment and has a first and a second segment, a lens holder assembly configured to locate and releasably coupled lenses within the reservoir and being coupled to the first segment, and a drive mechanism being coupled to the second segment and configured to selectively introduce a catalyst to the hydrogen peroxide solution.
US2012/0205255 describes an ozone-generating apparatus and use thereof for disinfecting contact lenses.
U.S. Pat. No. 5,252,291 described a device and method for cleaning and disinfecting contact lenses according to the principles of electrophoresis and electrolysis. A device of U.S. Pat. No. 5,252,291 comprises a contact lens containing well with two well electrodes spaced apart from each other for inserting one or two contact lens or lenses therebetween and a reservoir having one reservoir electrode and connected to the contact lens containing well via a narrow channel. In operation, for disinfecting contact lenses chlorine is generated electrolytically from chloride in the contact lens containing well by the generation of an electrical field between the two electrodes, and then the chlorine is removed from the contact lens containing well while being generated in the reservoir, by generating an electrical field between the well electrodes and the electrode in the reservoir. It was believed that the chlorine formed in the reservoir would have a long diffuse path across the ion permeable bridge, minimizing reintroducing the chlorine in the lens containing well. However, this patent does not disclose how much chlorine is produced at different times and how fast the chlorine is removed.
There is still a need for a simple lens care systems which can have microbial efficacy toward a broad spectrum of organisms including Acanthameoba. 